• be able to explain what type of tissue makes up the NS
• be able to describe the di erent roles of tissues in perceiving & behaving
Key Words:
(a) Bilaterally symmetrical - anterior & posterior ends and a right & left
side - description of the brain
(b) Cephalisation - nervous tissue becomes highly concentrated on one
end of an organism
(c) Brain - complex integrating centre are up of clusters of ganglia
(d) Ganglia - grouping of neurone cell bodies in PNS
(e) Nuclei/Centre - grouping of neurone cell bodies in the brain (CNS)
(f) Tracts - grouping of axons in the brain (CNS)
(g) Nerves - axons of a erent & e erent neurones
(h) Soma - neurone cell body
Explain what type of tissue makes up the NS
Cnidarians - unusual organism where neurones are not specialised unlike most NS's
where the neurones are split
into 3 types - sensory, relay &
motor. They still work together
to allow for some complex
behaviour - when
encountering a seashell its
tentacles grasp it and
performs a somersault
attaching its foot to the shell
before releasing its tentacles.
They also don't have
cephalisation like
Echinoderms.
ff ff ff
, Page 2 of 14
Vertebrate CNS -
• most highly cephalised and unique in that they have hollow dorsal nerve chords.
• Portion of the NS encased within cartilage or bone is the CNS (brain/spinal chord) -
everything else is PNS
Origin of Neural Tissue -
• both come from the same type of cell - Neural Stem Cells (NSC's).
• Stem cells are multipotent & self-renewing that can develop into di erent types of cells.
NSC's vital for neurogenesis (genesis of Neural Tissue) - mostly occurs in prenatal
development.
• Adult neurogenesis does occur - in adult mammals (inc. humans) - plasticity (explored
further in future lesson) - process of NSC's development in slide
Two types of Neural tissue/cells -
1. Neurones - processing, transfer, storage of info.
2. Neuroglia / Glial cells - support, regulation, protection and repair* of Neurons -
surround the neurons for said reasons
*Glial cells act as stem cells in some areas of brain promoting regrowth where possible, in
regions where uncontrolled regrowth may be detrimental they hinder regrowth of
damaged neurones.
ff
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